This invention relates to fuel processing which converts gasoline to hydrogen for use as a fuel reactant in a fuel cell, and more particularly to use of an aqueous antifreeze solution, in place of fuel processing system steam, in the fuel vaporizer during startup when the temperature is below freezing.
It is known that a fuel processing system for a low temperature fuel cell consists of a desulfurizer, a reformer, a shift converter and a selective oxidizer. The desulfurizer removes sulfur compounds from the fuel, the reformer reacts the fuel with water/steam and sometimes air to produce mainly hydrogen, carbon dioxide and carbon monoxide, the shift reactor reacts water/steam with carbon monoxide to produce hydrogen and carbon dioxide, and the selective oxidizer oxidizes the carbon monoxide with oxygen to produce carbon dioxide. Three primary types of reformers in current use include a steam reformer, an auto-thermal reformer and a partial oxidation reformer. The steam reformer, auto-thermal reformer and shift converter require water for the reactions to occur; the partial oxidation reformer does not use water. The auto-thermal reformer and the partial oxidation reformer also require air as a reactant.
The residual water inventory of a polymer electrolyte membrane fuel cell power plant may be on the order of several gallons. It requires many minutes to thaw such a quantity of ice. Fuel cell power plants utilized for vehicles have an objective to be started in about ten seconds. In colder climates, fuel cell power plants utilized in vehicles will require startup at sub-freezing temperatures. In any gasoline fuel processing system, steam must be provided to the vaporizer to vaporize the gasoline as a first step of the process. However, there is no method of storing water in the fuel cell power plant for use in the fuel processor that prevents the water from freezing.
Objects of the invention include: provision of a source of unfrozen water for use in the vaporizer of a gasoline fuel processing system; provision of a fuel cell power plant that can start in seconds in sub-freezing temperatures; and a fuel cell power plant suitable for use in vehicles, that can start quickly in sub-freezing temperatures.
According to the present invention, an aqueous antifreeze solution is substituted for the normal water input to a start-up heat exchanger that provides steam to the gasoline vaporizer within the gasoline fuel processing system. According to the invention, the aqueous antifreeze solution is converted to steam in the start-up heat exchanger, and the antifreeze component cleanly decomposes within the reformer and shift converter of the gasoline fuel processing system. According to the invention, suitable antifreeze solutions are: methanol-water, ethanol-water, glycerol-water, ethylene glycol-water and propylene glycol-water. Preferably these solutions are free of commonly-used additives and stabilizers.
The invention provides quick start-up of a fuel processing system suitable for use in vehicles powered by gasoline fueled fuel cell power plants.
Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawing.